Process of treating kryolith.



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PROCESS OF TREATING KRYOLITH.

SPECIFICATION forming part of Letters Patent No. 660,094, dated October23, 1900.

Application filed December 27, 1899.

T0 aZZ whom, it may concern:

Be it known that I, CHARLES A. DOREMUS, a citizen of the United States,residing in the borough of Manhattan, city, county, and State of NewYork, have invented a new and useful Process of Treating Kryolith, ofwhich the following is a specification.

The mineral kryolith is a double fluorid of aluminium and sodium, thechemical formula of which is AI F GNaF.

Although several different processes have been used for the chemicaltreatment of kryolith on a manufacturing commercial scale, the one nowchiefly employed consists of furnacing with lime. Sodium aluminate andcalcium fluorid result. The former is separated from the latter byleaching. The calcium fluorid is quite impure and is of little value.The fluorin, therefore,amounting to fifty-four per cent. of the weightof the kryolith, is not obtained in a serviceable form.

My object has been to devise a method for obtaining important fluorincompounds, while at the same time preserving the full value of the othercomponents of the kryolith. This new result I have accomplished byheating the kryolith in the presence of steam, as hereinafter set forth,to liberate hydrofluoric acid and leave a residue consisting either ofsodium aluminate or of a mixture of sodium fluorid and alumina or of amixture of sodium aluminate, sodium fluorid, and alumina.

I have found that when steam is allowed to act on kryolith at atemperature below its melting-point the kryolith and steam becomehydrofluoric acid and sodium aluminate; also, that when steam is allowedto act on molten kryolith hydrofluoric acid is set free and sodiumaluminate is formed until the increasing proportion of the lattersolidifies the molten mass; also, that when this solidified mass isfurther treated by steam sodium aluminate remains, while hydrofluoricacid escapes; also, that any of the above reactions can be brought aboutby the products of combustion of fuel consisting of or containinghydrogen, watery vapor or steam being the product or one of the productsof the combustion; also, that when kryolith is heated with steam thesilicon present is evolved as silicon fluorid, and thus removed from theSerial No. 741,710. (No specimens.)

alumina or aluminate; also, that when alumina or a hydrate, such asbauxite, is heated with kryolith and steam a soluble aluminate is formed and hydrofluoric acid escapes; also, that by the treatment withkryolith and steam even a greater proportion of alumina or a hydrate ofalumina than is needed to form an aluminate will be rendered soluble inacid or alkali 5 also, that when kryolith is heated with a hydrate, suchas aluminium hydrate, the steam evolved by the action of the heat on thehydrate Will react with the kryolith and hydrofluoric acid is set freeand sodium aluminate or sodium fiuorid and alumina, ora mixture ofthese, remains, together with alumina from the hydrate.

The above-mentioned chemical reactions may be carried out through theuse of diflerent mechanical devices, of which the following areillustrations:

I. Kryolith is placed in an iron retort and heated from the exterior.Steam is passed, hydrofluoric acid is disengaged, and sodium aluminateor sodium fluorid and alumina, or

a mixture of these, remains in the retort.

The reaction is controlled by the regulation of the heat and the passageof the steam. The products of the combustion of a fuel consisting of orcontaining hydrogen may be substituted for the externally-applied heatby allowing said products to pass through the retort or through an ovencontaining the kryolith.

II. Kryolith is placed in the hearth of a reverberatory furnace, and,when molten, steam is made to impinge on the molten mass. I-Iydrofluoricacid escapes abundantly until the mass stiffens through the productionof aluminate or of sodium fluorid and alumina, or a mixture of these.This solid residue is then subjected to further treatment with heat andsteam or heated with the products of combustion containing steam.

III. Kryolith is heated in a mechanical fur nace by a fuel consisting ofor containing hydrogen. The processing may be made to convert a part orthe whole of the fluorin into hydrofluoric acid. In this case I havefound it advantageous to add alumina or bauxite in order to preventballing and to obtain an aluminate containing a high pro portion ofalumina.

An excess of alumina or bauxite. above the proportion needed to form thealuminate will under this treatment be rendred soluble in acidor'alkali. The mechanical disintegration of infusible aluminate helps tocomplete the removal of the fluorin.

IV. Kryolith is made into briquets with an aluminium hydrate, such asbauxite, and these are heated in a furnace or oven either with orwithout the addition of steam or of steam produced by the combustion ofa fuel consisting of or containing hydrogen. Hydrofluoric acid isevolved, and the residue consists of sodium aluminate or sodium aluminate and alumina or sodium fiuorid and alumina, or a mixture of these.When only a part of the fiuorin is removed from the kryolith in any ofthe foregoing cases, the remainder may be converted to calcium fiuoridby heating with lime.

V. Kryolith is placed in a muffle-furnace, lined with material whichwill not be acted on by the fused mass, and is melted. Steam is thenmade to impinge upon or to pass through the molten kryolith so long asthe mass remains fluid. Hydrofluoric acid escapes, and the residue, whenwithdrawn, is treated either for the conversion of the fluorin remainingin it into hydrofluoric acid .or is otherwise processed, as deemedexpedient.

1 several modes of conducting the same, what I claim as new, and desireto secure by Letters Patent, is

1. The process of treating kryolith which consists in heating thekryolith, in the presence of steam, to a temperature below a white heat,substantially as described.

2. The process of converting kryolith into sodium aluminate andhydrofluoric acid,

which consists in passing steam through or over and into contact withthe kryolith at a temperature below a white heat, substantially asdescribed.

3. The process of treating kryolith to 0bj tain hydrofluoric acid,sodium fluorid and alumina, which consists in heating the kryo- Llith inthe presence of steam, and at a temperature below the melting-point ofkryolith, substantially as described.

CHARLES A. DOREMUS.

Witnesses:

A. W. WILKINSON, H. S. BoWLEs.

